Biomass refining (or biorefining) has become more prevalent in industry. Cellulose fibers and sugars, hemicellulose sugars, lignin, syngas, and derivatives of these intermediates are being utilized for chemical and fuel production. Indeed, we now are observing the commercialization of integrated biorefineries that are capable of processing incoming biomass much the same as petroleum refineries now process crude oil. Underutilized lignocellulosic biomass feedstocks have the potential to be much cheaper than petroleum, on a carbon basis, as well as much better from an environmental life-cycle standpoint.
Lignocellulosic biomass is the most abundant renewable material on the planet and has long been recognized as a potential feedstock for producing chemicals, fuels, and materials. Lignocellulosic biomass normally comprises primarily cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are natural polymers of sugars, and lignin is an aromatic/aliphatic hydrocarbon polymer reinforcing the entire biomass network. Some forms of biomass (e.g., recycled materials) do not contain hemicellulose.
Despite being the most available natural polymer on earth, it is only recently that cellulose has gained prominence as a nanostructured material, in the form of nanocrystalline cellulose (NCC), nanofibrillar cellulose (NFC), and bacterial cellulose (BC). Nanocellulose is being developed for use in a wide variety of applications such as polymer reinforcement, antimicrobial films, biodegradable food packaging, printing papers, pigments and inks, paper and board packaging, barrier films, adhesives, biocomposites, wound healing, pharmaceuticals and drug delivery, textiles, water-soluble polymers, construction materials, recyclable interior and structural components for the transportation industry, rheology modifiers, low-calorie food additives, cosmetics thickeners, pharmaceutical tablet binders, bioactive paper, pickering stabilizers for emulsion and particle stabilized foams, paint formulations, films for optical switching, and detergents.
Biomass-derived pulp may be converted to nanocellulose by mechanical processing. Although the process may be simple, disadvantages include high energy consumption, damage to fibers and particles due to intense mechanical treatment, and a broad distribution in fibril diameter and length.
Biomass-derived pulp may be converted to nanocellulose by chemical processing. For example, pulp may be treated with 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) to produce nanocellulose. Such a technique reduces energy consumption compared to mechanical treatment and can produce more uniform particle sizes, but the process is not regarded as economically viable.
Improved processes for producing nanocellulose from biomass at reduced energy costs are needed in the art. Also, improved starting materials (i.e., biomass-derived pulps) are needed in the art for producing nanocellulose. It would be particularly desirable for new processes to possess feedstock flexibility and process flexibility to produce either or both nanofibrils and nanocrystals, as well as to co-produce sugars, lignin, and other co-products. For some applications, it is desirable to produce nanocellulose with high crystallinity, leading to good mechanical properties of the nanocellulose or composites containing the nanocellulose. For certain applications, such as nanocellulose-polymer composite materials, it would be beneficial to increase the hydrophobicity of the nanocellulose.
High-impact polystyrene (HIPS) is a low-cost plastic material that is easy to machine and fabricate. HIPS is often specified for structural applications when impact resistance, machinability, and low cost are required. It is frequently used machining pre-production prototypes since it has excellent dimensional stability and is easy to fabricate, paint and glue. Applications include medical packaging, food trays and containers, electronics, lids, plates, trays, patterns, and forms. Improvements to HIPS are desired.